Executive summary
Although South Korea has often been seen as missing in action regarding conversations around a Taiwan Strait contingency, since at least 2021, its leaders have openly acknowledged the importance of peace and stability in the Taiwan Strait. Nevertheless, the perception persists that South Korea remains more cautious than other U.S. allies in discussing its role in a Taiwan Strait contingency. South Korea’s reluctance to define its role is understandable given its focus on the defense of the Korean Peninsula and its close economic relationship with China. Acknowledging these political sensitivities, the Biden administration encouraged but did not push Seoul to engage in more concrete discussions related to Taiwan.
That approach may change if the second Trump administration decides to double down on deterrence against China and bolster its commitment to Taiwan. It remains unclear how U.S. President Donald Trump will engage Taiwan in his second term, especially if he seeks to make a deal with Chinese President Xi Jinping. Yet, the China hawks within his administration may be more inclined to press allies to deepen their commitment to Taiwan’s defense. In such a scenario, the United States may push South Koreans outside of their comfort zone to provide more clarity and pledge robust support for the U.S.-South Korea alliance in the event of a Taiwan Strait contingency. However, if Trump takes steps that undermine South Korean security interests, including meeting Kim Jong Un without consulting Seoul or calling for the withdrawal of U.S. troops, Seoul may be less willing to support the Trump administration’s stances toward China and Taiwan.
South Korea recognizes Taiwan’s importance
The increasingly linked nature of geopolitical conflict and the rising relevance of economic security in an era of weaponized interdependence means that Taiwan’s relevance for South Korean security will continue to grow. South Korea has come to publicly acknowledge this reality, voicing its concerns over tensions around Taiwan when U.S. President Joe Biden and then-South Korean President Moon Jae-in included language emphasizing “the importance of preserving peace and stability in the Taiwan Strait” for the first time in a bilateral joint summit statement. Despite Chinese pushback in response to the language, South Korean officials continued to reaffirm Seoul’s support for peace and stability across the Taiwan Strait through trilateral statements alongside Washington and Tokyo at the East Asia Summit and Camp David, and in defense and foreign ministerial meetings under the Biden and second Trump administrations. At the presidential level, South Korean President Yoon Suk-yeol has called the Taiwan issue “a global issue” rather than “simply an issue between China and Taiwan” and the preservation of peace and stability in the Taiwan Strait “an essential element in security and prosperity in the Indo-Pacific region.” While Beijing accused Yoon of equating the Taiwan issue with the situation on the Korean Peninsula, Seoul summoned China’s ambassador to protest Beijing’s “diplomatic discourtesy.”
Whether led by a conservative or progressive government, Korean policymakers will have to bear in mind the costs and implications of a Taiwan Strait conflict for South Korea’s national interest. More than 90% of South Korea’s maritime trade passes through the Taiwan Strait and the South China Sea. Any disruption of freedom of navigation, whether caused by a Chinese blockade or an all-out war in the Taiwan Strait, would damage South Korea’s economy, reducing the nation’s GDP by 23%. Additionally, even though South Korean and Taiwanese chipmakers may see each other as competitors, South Korean industries still rely on supply chains flowing through Taiwan in the production process, highlighting their symbiotic relationship. Finally, South Koreans have expressed increasing concern about the spillover effects of a Taiwan Strait conflict onto the Korean Peninsula. A war over the Taiwan Strait, which might require some United States Forces Korea (USFK) resources to be diverted to Taiwan, would leave South Korea more vulnerable to North Korean provocations.
South Korea must also consider the economic and diplomatic fallout with China should it take a stand in support of Taiwan’s defense. South Korea seeks to avoid crossing Beijing’s red lines over the Taiwan issue and to maintain positive relations with its larger neighbor. However, the Yoon government has also asserted that Beijing must respect Seoul’s sovereignty and national interest. Although Beijing claims Taiwan as its core interest, any unilateral attempt to change the status quo could potentially harm South Korean national interests. Thus, beyond offering statements of support for peace and stability on the Taiwan Strait, Seoul must seriously consider potential crisis scenarios and its own role and level of engagement with the United States in a cross-Strait contingency.
Should South Korea pursue strategic ambiguity or clarity?
Although South Korean officials privately acknowledge that they support the United States as an ally and would play some role in a conflict between Taiwan and China, that role remains undefined. Understandably, the role of the U.S.-South Korea alliance and South Korea’s involvement would be contingent on the scale, scope, and conditions under which conflict erupts. A direct, unprovoked People’s Liberation Army (PLA) attack on Taiwan and U.S. bases in South Korea would likely draw Seoul’s participation in the conflict. Meanwhile, coercive actions against Taiwan at the low end of the conflict spectrum—such as a naval blockade without directly targeting the United States and its allies—may elicit South Korea’s economic or diplomatic support for Taiwan, but not necessarily direct military intervention.
Recent calls for South Korea to adopt a bolder position on Taiwan have grown in part as other U.S. regional allies, including Australia and Japan, have become increasingly more forward-leaning on coordinating regional defense. Washington, Tokyo, and Canberra have engaged in discreet, early-stage contingency planning and discussions over Taiwan, given that all three are most likely to contribute forces, grant basing access to the United States, and/or pursue more defensive roles in potential contingency scenarios. In comparison, Seoul has remained vague about whether and how it would participate in U.S. efforts to counter malign Chinese activities in the region, given South Korea’s reliance on China for trade and diplomacy with North Korea.
To the extent that a Taiwan Strait conflict implicates the U.S. military and the U.S.-South Korea alliance and given that a war in Taiwan could also create a greater risk of conflict on the Korean Peninsula, Seoul and Washington should consider enhancing coordination on Taiwan beyond unofficial, Track 2 dialogues. Conversations can proceed discreetly and privately given Seoul’s sensitivities to discussing its response to hypothetical scenarios in Taiwan. Three areas in particular should be addressed to clarify the role and scope of the U.S.-South Korea alliance and the boundaries of South Korea’s engagement in a Taiwan Strait contingency.
First, Washington and Seoul should define in more concrete terms what “strategic flexibility“ (i.e., the use of USFK in operations outside of the Korean Peninsula) would look like in practice, in the event of a Taiwan Strait contingency. In 2006, Seoul acknowledged Washington’s desire for strategic flexibility and Washington agreed to respect South Korea’s position that U.S. forces would “not be involved in a regional conflict in Northeast Asia against the will of the Korean people.”
This formulation of strategic flexibility has remained for two decades, but without specifying how USFK might actually be deployed in response to the expanded role and responsibilities of the U.S.-ROK alliance for the broader Indo-Pacific. Would South Korea grant permission ahead of time to permit U.S. forces to support combat operations, or at the very least, participate in non-combat operations in the Taiwan Strait? Under what conditions might USFK be deployed to Taiwan, and how might the Combined Forces Command ensure defense and deterrence on the Korean Peninsula in light of a possible counterattack from China or provocations from North Korea? Even if USFK were not deployed outside of the Korean Peninsula, the U.S. military would want to make use of its existing bases and facilities in South Korea. This could include Camp Humphreys in Pyeongtaek, which the U.S. Army described as “the largest power projection platform in the Pacific.” U.S. air bases in Osan and Kunsan could also be relevant in a prolonged Taiwan Strait contingency, as well as South Korea’s Busan Naval Base, which includes ports and the hosts Commander, Naval Forces Korea headquarters.
Second, Washington and Seoul should clarify what military contributions South Korea might provide in a Taiwan Strait contingency. At the low end of the spectrum, South Korea could provide rear-area support, including intelligence sharing and assistance on non-combat evacuations from Taiwan. South Korea could also provide logistical support, helping U.S. ships and planes refuel. Taking a step further, South Korea could offer precision-guided munitions, including cruise missiles, Stingers, and Javelins, to the United States to help backfill weapons for Taiwan.
Although there are some scenarios—such as a direct PLA attack on Taiwan, American, and allied forces—that might justify major combat involvement from South Korea, for the most part, it would be unrealistic for South Korea to participate in such high-intensity combat operations. Nevertheless, as our colleague Ryan Hass has argued, South Korea might be willing to step up and assume responsibilities for the maritime defense of the Korean Peninsula or even deploy its own forces in defense of Taiwan if the PLA preemptively attacked U.S. bases in South Korea without warning. Lastly, improving coordination between USFK and United States Forces Japan (USFJ) and resolving issues related to the chain of command across USFK and United States Indo-Pacific Command might reduce potential logistical bottlenecks. This would better prepare the United States and its allies for a possible contingency on the Taiwan Strait that would involve U.S. forces across the Indo-Pacific theater.
Third, beyond military contingency planning, Seoul and Washington should discuss steps to boost peace, stability, and deterrence in the Taiwan Strait. Consistent messaging on Taiwan between Washington and its allies, including Seoul, could help ensure stability. Although Seoul and Washington have slightly different ambiguous interpretations of the “One China” principle, both sides can agree that any unilateral change of the status quo in Beijing or Taipei remains unacceptable. South Korea could also help boost Taiwan’s psychological confidence by consistently recognizing and framing conflict on the Taiwan Strait as a matter of global concern. To some degree, Seoul has already begun adopting this narrative by recognizing the links and parallels across theaters in Europe, the Indo-Pacific, and the Middle East.
Improving South Korea-Taiwan relations
The recent trend toward increased allied and global support for Taiwan—coupled with the Trump administration’s expectation that South Korea should play a larger role in the Indo-Pacific—presents an opportunity for Seoul to rethink its approach to Taiwan. Although Seoul may not want to damage relations with Beijing over hypothetical scenarios, stability on the Taiwan Strait remains essential to South Korean economic security. Strong anti-China sentiment among the South Korean public across generations may also provide Seoul greater domestic political cover to increase its support for Taiwan.
Improved relations between South Korea and Taiwan could also help boost Taipei’s morale while building Seoul some leverage vis-à-vis Beijing. Economic and technological ties between the two sides have the most promise, given their shared strengths in innovation. South Korea and Taiwan should continue coordinating to safeguard and diversify semiconductor supply chains from potential shocks, to protect their competitive advantages in the critical technology. Since the pandemic, South Korea has increased its parliamentary delegation visits to Taiwan. The chair of the Korea-Taiwan Parliamentarian Friendship Association, Cho Kyoung-tae, led a delegation visit to Taipei in December 2022 and again in May 2024 to attend the inauguration ceremony of Taiwan President Lai Ching-te. Despite pushback from China, many democracies, including Japan, the Czech Republic, Lithuania, Germany, and the United States, are also continuing the cadence of parliamentary-level visits to Taiwan. As Seoul’s partners continue these visits, Seoul should have space to bolster ties and feel comfortable about engaging Taipei on overlapping issues.
Conclusion
Trump’s recent heated exchange with Ukrainian President Volodymyr Zelenskyy in the Oval Office regarding security guarantees for Ukraine (or the lack thereof) raises uncertainty about the reliability of U.S. support to Taiwan and other allies and partners in the Indo-Pacific. It would certainly be difficult to expect Seoul to raise the ante on Taiwan’s defense if Washington itself remains unwilling to defend Taiwan. Seoul may, therefore, take a wait-and-see approach for now, given domestic political uncertainties at home and Trump’s unpredictable approach to U.S. allies and partners in Asia, including Taiwan.
The volatile geopolitical environment of the last few years has demonstrated that tensions in the Taiwan Strait cannot be ignored. Although Trump has yet to clarify his policy toward Taiwan, his administration’s professed prioritization of the Indo-Pacific suggests that he is prepared to compete against China on multiple fronts. South Korea, too, must remain ready to play a larger role in the Indo-Pacific, including on the Taiwan Strait, and coordinate its strategy with the United States and other allies and partners in the region.
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